There are different constructive forms of piezoelectric axial transducers mainly having a cylindrical housing having a seismic mass inside which by its vibratory movement inertial tendency of a seismic mass to maintain the state and moving direction, exercises a pulsating pressure on a disk or on a package of piezoelectric disks, in order to transform in a linear way the pulsating impulses of the seismic mass into impulses of an electric voltage generated by a piezoelement.
These transducers show the following disadvantages:
The inactive mass, predominantly its housing, is heavier than the seismic mass (representing the active element) thus altering the vibrating movements that should be detected in the case of small-dimension parts, the vibration frequency and amplitude depending on the mass of the element in motion;
to reduce the ratio between the transducer inactive weight and its active weight (i.e. of the seismic mass). The latter is made of rare metal alloys whose price is high, like wolfram, osmium, iridium.